Conventionally, sensor units in the form of revolution rate sensors in motor vehicles, for example for an antilock brake system (ABS) of an electronic brake system of a motor vehicle, are used to detect the rotation rate of a wheel and to control associated braking depending on rotary motion and the rotation rate. For this purpose, values measured by the sensor unit are transferred to an analyzer via at least two connecting lines. One such sensor unit is for example featured in DE 10 2006 021 018 B4.
In the wheel area of a motor vehicle, however, electrostatic charging occurs within individual electrically isolated parts of the motor vehicle. The electrostatic charging arises for example through the friction of the tires while travelling. Because the chassis parts, in particular vehicle axles, include no conductive connection to the frame of the vehicle, electrostatic charges cannot be discharged from the vehicle axle, as a result of which there is a continuous raised potential between the vehicle axle and the frame of the vehicle. On exceeding a voltage limit, a flashover of the charge to the nearest electrically conductive part takes place. Such flashovers occur in particular in the region of connecting lines between electrical sensor units and electronic analyzers.
Electric circuits with integrated components, such as those used in analyzers, in particular in control units for electronic brake systems, are however sensitive to large noise voltages that can occur because of electrostatic discharges (electrostatic discharge—ESD) in individual vehicle parts. If such overvoltages occur above an upper tolerance limit of a maximum permissible voltage of the analyzer, the analyzer can be damaged.
In order to protect electrical circuits, such as analyzers in control units, against overvoltages, conventionally overvoltage protection devices, such as direct surge arresters, are used that make an electrically conductive connection between otherwise electrically decoupled vehicle parts and thereby discharge any possible electrostatic charges.
DE 9412038 U1 discloses a device for connecting a sensor to a chassis of a vehicle. The sensor comprises, in addition to two conductive wires that can be connected to an analyzer, a third conductive wire that is connected to ground (GND). For this purpose, the sensor is enclosed by a covering body of non-conducting plastic from which the third conductive wire protrudes. The covering body with the protruding third conductive wire is at least partly enclosed by a further covering body of conductive plastic, wherein the sensor is attached to a wheel mounting via the further covering body such that the wheel mounting is conductively connected to ground via the third conductive wire.
However, such surge arresters require a cost intensive overhead, because an additional line is provided that requires a change from standardized control units and entails greater maintenance effort for the vehicle electronics.